1. Field of the Invention
The present invention relates to a twin-drum type continuous casting apparatus provided with a vibration exciting means in a side weir.
2. Description of the Prior Art
A twin-drum type continuous casting apparatus has a basin formed by a pair of rotary cooling drums and a pair of side weirs pressed to both the end surfaces of these drums. While molten metal is being fed to this basin, a belt-like cast piece is ejected downwards from the gap between the cooling drums. It has heretofore been the practice to cause the side weir to vibrate along the end surface of the cooling drum for the purpose of preventing a solidified shell from fixedly securing to the side weir.
In the following, description will be made of a side weir vibrating device in a twin-drum type continuous casting apparatus in the prior art with reference FIGS. 3 and 4. FIG. 3 is a side view of the side weir vibrating device, in which an essential portion is partly cut away, and FIG. 4 is a cross-sectional view taken along line IV--IV in FIG. 3 as viewed in the direction of the arrows.
In this casting apparatus, side weirs 52 are pressed against a pair of cooling drums 51 by means of pressing devices 42 via vibrating plates 31, and a basin is thereby formed in the space delimited by the pair of drums 51 and the side weirs 52 on opposite sides thereof. The cooling drums 51 rotate while being held in sliding contact with refractory materials 53 on the surfaces of the side weirs 52. On the rear surface of the vibrating plate 31 fixed to each side weir 52 are provided a bearing 37 and a guide 34. Within the guide 34 is fitted a slider 33 so as to be slidable in the vertical direction along the guide. A support shaft 36 is fixedly provided on a frame 41 and is rotatably inserted in the bearing 37. An eccentric tip end portion of a vibration exciting shaft 32 is rotatably supported from the frame 41 and pivotably mounted to the slider 33. In this way, when the vibration exciting shaft 32 is rotated by means of a driving unit (not shown), the slider 33 vibrates the vibrating plate 31 about the support shaft 36 while sliding within the guide 34.
In a continuous casting operation, the pair of cooling drums 51 are rotated in the direction of the arrows shown thereon, the side weirs 52 are pressed against the opposite end surfaces of the cooling drums 51 by means of the pressing devices 42, and while the side weirs 52 are vibrated about the support shafts 36 in the direction of the arrows shown at the location of the guide 34 in FIG. 4, molten metal is fed from a gate (not shown) disposed above the above-described basin into the basin. Then, molten metal 61 in the basin is cooled by the cooling drums 51, and thereby a solidified shell is formed on the surface, while a belt-like cast piece 62 is ejected from below. At that time, by vibrating the side weirs 52, the solidified shell is prevented from fixedly securing to the refractory materials 53 on the surfaces of the side weirs 52.
In the above-described side weir vibrating device in the prior art, due to the fact that the support shaft 36 is disposed lower than the position of the minimum gap space between the rotary cooling drum 51 (hereinafter called the "kissing point") and that the vibrating shaft 32 is disposed in the middle between molten metal surface 60 and the kissing point, the side weir 52 is reciprocated in the lateral direction by the vibrating shaft 32 disposed in the vicinity of its center of gravity, and is rotated about the support shaft 36 under the kissing point.
Since the vibration exciting force generated by the vibrating shaft 32 for the side weir 52 is applied in the vicinity of the center of gravity of the side weir 52, because of the large moment of inertia due to rotation of the side weir 52 about the support shaft 36 upon high-speed vibration, the side weir 52 would vibrate also in the axial direction of the cooling drums 51, and hence there is a shortcoming in that a gap clearance is produced momentarily between the refractory material 53 of the side weir 52 and the end surfaces of the cooling drums 51, and at the next moment the refractory material 53 would collide against the end surfaces of the cooling drums 51, and thereby run-out Would be generated in a cast piece, or the life of the refractory material would be shortened.